1. Field of the Invention
The present invention relates to demulsifiers, for breaking water-in-oil emulsions, which contain alkoxylated alkyl polyglycosides and a method of breaking water-in-oil emulsions using such demulsifiers.
2. Discussion of the Background
The extraction of petroleum from underground reservoirs often results in water-in-oil emulsions which are usually very stable. The active emulsifiers are surface-active constituents within the petroleum, which are particularly concentrated in the petroleum resins and asphaltenes. Since the petroleum emulsions always have a much higher viscosity than that of the oil, transport thereof would mean a correspondingly higher pumping power. It is therefore necessary to break them as a step in the petroleum preparation process before transport. In addition, the disperse phase consists of salt water which usually has a high chloride content which would lead to considerable corrosion problems in refinery processing. The water must therefore be removed as substantially as possible. This is usually carried out by adding small amounts of demulsifiers (emulsion breakers) in the presence of heat. Good demulsifiers lead to as near quantitative oil/water separation as possible with, as far as possible, low use concentrations, low temperatures and short action time. The composition of petroleum varies widely throughout the world, and this also applies to the emulsifiers of the petroleum emulsions. Accordingly, the structures of the demulsifiers also have to be optimized for each petroleum emulsion.
Frequently used at present is demulsification using products of the reaction of alkylene oxides with alkylphenol/formaldehyde resins such as described, for example, in DE-A 20 13 820 and 31 42 955 and U.S. Pat. No. 2,560,333. Another important group of demulsifiers are ethylene oxide/propylene oxide block copolymers as described, for example, in DE-A 10 18 179 and 15 45 250. Another class of petroleum emulsion breakers consists of alkoxylated polyamines (DE-A 22 27 546 and EP-A 147 743). Finally, emulsifiers based on alkoxylated diisocyanates (DE-A 20 59 707) and bisglycidyl ethers (EP-A 55 434) are also described.
The disadvantage of the above-described demulsifiers is their extremely high specificity. That is to say a given structure or composition of demulsifier is suitable only for one reservoir, and in some cases even for only one sector. Other disadvantages, which are now very significant, are ecological in nature. Thus, the biodegradability of the above-described demulsifiers is usually completely inadequate and their aquatoxicity is considerable. The latter property is of great importance particularly in off-shore fields.
Thus, there remains a need for demulsifiers for breaking petroleum emulsions which can be employed under various reservoir conditions and, moreover, have, in particular, a high biodegradability and a low toxicity.